/Engine/Source/Runtime/UMG/Public/Blueprint/SlateBlueprintLibrary.h
Translates a screen position in pixels into absolute application coordinates. If bIncludeWindowPosition is true, then this method will also remove the game window's position (useful when in windowed mode).
static void ScreenToWidgetAbsolute ( [UObject](API\Runtime\CoreUObject\UObject\UObject) * WorldContextObject, FVector2D ScreenPosition, FVector2D & AbsoluteCoordinate, bool bIncludeWindowPosition )